Preservative compositions for wood products

ABSTRACT

Preservative compositions for wood products are described. The compositions include at least one boron-containing material, such as but not limited to boric anhydride, and at least one silane-containing material, such as but not limited to methyltrichlorosilane. Optionally, at least one solvent, such as tetrahydrofuran, pentane, or water, may also be employed in the compositions. The compositions impart protection to the treated wood products, especially damage caused by exposure to water and insects.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 10/297,398, entitled“Preservative Compositions for Wood Products”, filed May 27, 2003.

BACKGROUND OF THE INVENTION

The present invention relates generally to wood product preservatives,and more particularly to wood product preservative compositionsincluding at least one boron-containing material and at least onesilane-containing material.

The use of wood products, such as lumber, in modern society is extremelywidespread. For example, wood products are found in housing constructionmaterials, crating materials, telephone pole materials, fencingmaterials, indoor and outdoor furniture, as well as many otherapplications.

Although wood is an extremely useful and versatile material to employwith respect to the afore-mentioned applications, it does suffer fromcertain disadvantages. This is especially true with respect to woodproducts that are used primarily for outdoor applications.

For example, wood, especially untreated wood, is susceptible to damagecaused by the elements, especially water, as well as insects (e.g.,termites, certain types of ants, and other boring insects).

Water damage typically causes wood products to warp, crack, check, aswell as become discolored and mildewed. Insect damage typically causeswood products to rot and decay. Typically, water and/or insect damageleads to the eventual replacement of the damaged section of wood atgreat expense, effort, and inconvenience.

Although wood preservative and protectant manufacturers have marketedvarious wood treatment products to supposedly prevent, or reduce thelikelihood of, the occurrence of water and insect damage to woodproducts, these products have not been completely satisfactory,especially with regard to effectiveness, cost concerns, ease ofapplication, duration of treatment time, and duration of protectionafforded.

Therefore, there exists a need for preservation compositions for variouswood products that will provide satisfactory protection against waterand insect damage, as well as being highly effective, relativelyinexpensive, relatively easy to apply, have a relatively short treatmenttime, and provide a relatively long period of protection.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide new and improvedpreservative compositions for wood products and methods for using same.

It is another object of the present invention to provide new andimproved preservative compositions for wood products and methods forusing same, wherein the preservative compositions protect the woodproducts against water damage and/or insect damage.

It is another object of the present invention to provide new andimproved preservative compositions for wood products and methods forusing same, wherein the preservative compositions contain at least oneboron-containing material and at least one silane-containing material.

It is another object of the present invention to provide new andimproved preservative compositions for wood products and methods forusing same, wherein the preservative compositions contain at least oneboron-containing material, at least one silane-containing material, andat least one solvent.

It is another object of the present invention to provide new andimproved preservative compositions for wood products and methods forusing same, wherein the preservative compositions contain boricanhydride and methyltrichlorosilane.

It is another object of the present invention to provide new andimproved preservative composition for wood products and methods forusing same, wherein the preservative compositions contain boricanhydride, methyltrichlorosilane, and tetrahydrofuran.

In accordance with one embodiment of the present invention, apreservative composition for wood products is provided, comprising: (1)at least one boron-containing material; and (2) at least onesilane-containing material.

In accordance with a second embodiment of the present invention, apreservative composition for wood products is provided, comprising: (1)boric anhydride; and (2) methyltrichlorosilane.

In accordance with a third embodiment of the present invention, a methodfor protecting a wood product is provided, comprising: (1) providing acomposition comprising at least one boron-containing material and atleast one silane-containing material; and (2) contacting the woodproduct with the composition.

In accordance with a fourth embodiment of the present invention, amethod for protecting a wood product is provided, comprising: (1)providing a first composition comprising at least one boron-containingmaterial; (2) contacting the wood product with the first composition;(3) providing a second composition comprising at least onesilane-containing material; and (4) contacting the wood product with thesecond composition.

A more complete appreciation of the present invention and its scope canbe obtained from the following detailed description of the invention andthe appended claims.

DETAILED DESCRIPTION OF THE INVENTION

The present invention includes compositions, and method of use therefor,for preserving, protecting, and treating wood and wood products so as toimpart protection against various sources of damage, including, but notlimited to water and/or insects. The terms “preserving,” “protecting,”and “treating,” as those terms are used interchangeably herein, aremeant to include any methods of, and compositions for, protecting woodand wood products from damage caused by any source, including, but notlimited to water and/or insects. The terms “wood” and “wood products,”as those terms are used interchangeably herein, are meant to include anyobject containing any amount of wood.

In accordance with one preferred embodiment of the present invention,the preservative composition consists primarily of at least oneboron-containing material and at least one silane-containing material.

The boron-containing material is preferably in the form of boricanhydride (chemical formula: B₂O₃), although other forms ofboron-containing materials are acceptable. By way of a non-limitingexample, borax (chemical formula: Na₂B₄O₇.10H₂O), and disodiumoctaborate tetrahydrate (chemical formula: Na₂B₈O₁₃.4H₂O) may be used aswell. Effective fungal and fire resistance can be obtained with a boronloading of 0.1 weight percent, based on the total weight of the treatedwood product. However, in order to prevent wood-boring insectinfestation (e.g., by ants and termites), a loading of 1-2 weightpercent of boron is generally required. For more problematic insects,such as the Formosan termite, a loading of 7 weight percent of boron isgenerally required. Therefore, the present invention provides a product,and method of using same, to introduce boron into the wood product atlevels of at least about 0.1 to at least about 7 weight percent and sealit to prevent environmental factors (e.g., rain) from leaching it fromthe interior of the treated wood product.

Silanes are generally defined a class of silicon-based materials,analogous to alkanes, that is, straight-chain, saturated paraffinhydrocarbons having the general formula Si_(N)H_(2N+2), wherein N is aninteger equal to 1 or higher. The silane-containing material ispreferably in the form of trichloromethylsilane (chemical formula:CH₃CI₃Si), although other forms of silane-containing materials areacceptable. Examples of other silane-containing materials useful inpracticing the present invention include, without limitation:

-   (Chloromethyl) Trichlorosilane;-   [3-(Heptafluoroisoproxy)Propyl]Trichlorosilane;-   1,6-Bis(Trichlorosilyl)Hexane;-   3-Bromopropyltrichlorosilane;-   Allylbromodimethylsilane;-   Allyltrichlorosilane;-   Bromomethylchlorodimethylsilane;-   Bromothimethylsilane;-   Chloro(Chloromethyl)Dimethylsilane; Chlorodiisopropyloctylsilane;-   Chlorodiisopropylsilane;-   Chlorodimethylethylsilane;-   Chlorodimethylphenylsilane;-   Chlorodimethylsilane;-   Chlorodiphenylmethylsilane;-   Chlorotriethylsilane;-   Chlorotrimethylsilane;-   Dichlorodimethylsilane;-   Dichloromethylsilane;-   Dichloromethylvinylsilane;-   Diphenyldichlorosilane;-   Di-t-Butylchlorosilane;-   Ethyltrichlorosilane;-   Lodotrimethylsilane;-   Pentyltrichlorosilane;-   Phenyltrichlorosilane;-   Trichloro(3,3,3-Trifluoropropyl)Silane;-   Trichloro(Dichloromethyl)Silane; and-   Trichlorovinylsilane.

In accordance with a highly preferred embodiment of the presentinvention, the preservative composition consists primarily of at leastone boron-containing material, at least one silane-containing material,and at least one solvent.

The solvent is preferably in the form of tetrahydrofuran (THF), althoughother solvents are acceptable. For example, hydrocarbons, which areliquid at room temperature, are acceptable. Examples of thesehydrocarbons include, without limitation, pentane, hexane, and heptane.

The preparation of an illustrative preservative composition, inaccordance with the general teachings of the present invention, ispresented in Example I, below:

EXAMPLE I

Approximately 50 ml of THF was added to a 250 ml Erlenmeyer flask.Approximately 1.0 gm of boric anhydride (B₂O₃) was added to the flaskand stirred. The mixture was cloudy at first, but gradually cleared uponsitting for 5 minutes. A small amount of B₂O₃ remained on the bottom ofthe flask. Approximately 10 to 15 ml of trichloromethylsilane was thenslowly added to the solution. No visual evidence of an exothermicreaction was observed. The solution remained clear.

In order to determine the effectiveness of the illustrative preservativecomposition prepared in Example I, a comparison test was performedbetween a treated portion and an untreated portion of a piece of plywoodboard. The results of the comparison test are presented in Example II,below:

EXAMPLE II

An eyedropper was used to deposit several drops of the preservativecomposition prepared in Example I to a piece of plywood board. Noevidence of an exothermic reaction or the evolution of foul smelling HCIgas was observed with the addition of the prepared solution to the woodsample. The composition diffused laterally across the surface of theboard in addition to vertically through the board. Water was poured ontothe treated area and it effectively repelled the water. The water wasimmediately absorbed in the untreated portion. Several drops were alsodeposited on the edge of the board to determine the effect of thesolvent (i.e., THF) on the glue. A screwdriver and a spatula were usedto try to separate the layers. This effort was unsuccessful.

In order to further determine the effectiveness of the illustrativepreservative composition prepared in Example I, a comparison test wasperformed between a treated portion and an untreated portion of a pieceof hardwood. The results of the comparison test are presented in ExampleIII, below:

EXAMPLE III

Several drops of the preservative composition prepared in Example I wereapplied to a solid piece of hardwood. The sample was allowed to sit forseveral minutes prior to exposing it to water. Upon drying, no whiteresidue was observed on the surface of the sample. Water was repelledoff both sides of the sample even though just one side was treated.

The preparation of another illustrative preservative composition, inaccordance with the general teachings of the present invention, ispresented in Example IV, below:

EXAMPLE IV

20 ml of THF was added to a 100 ml beaker. Approximately 1 gm of B₂O₃and 1 ml of trichloromethylsilane was added to the THF solvent. Thetotal volume was approximately 22 ml.

In order to determine the effectiveness of the illustrative preservativecomposition prepared in Example IV, a comparison test was performedbetween a treated portion and an untreated portion of a piece of plywoodboard. The results of the comparison test are presented in Example V,below:

EXAMPLE V

A piece of plywood, ⅝ inches×⅝ inches×3½ inches was placed into a beakerand partially submerged into the preservative composition prepared inExample IV. The beaker was covered for approximately 5 minutes. After 5minutes, the piece of plywood was removed and allowed to air dry. Thevolume of the preservative composition remaining in the beaker had beenreduced by 2-3 ml, or about 10%. There was no visible white deposit onthe surface of the plywood. Surface samples were removed from both thetreated and untreated portions of the plywood in order to evaluate themunder a microscope. There was an observable difference between thesamples. The treated plywood appeared as though it had been coated inglass or white cotton coating. There was a difference in the appearanceof the heartwood and the sapwood. The cells of the untreated plywoodappeared empty, while those of the treated wood appeared to be coatedwith glass. When drops of methanol were added to the plywood samples,the treated sample beaded up and looked like a jelly on the surface ofthe sample. Whereas, the run off water was readily absorbed on theuntreated plywood. A piece (½ inch×½ inch×¾ inches) of this plywood wasplaced in a 100 ml beaker containing 10 ml of water and covered with awatch glass. The sample was allowed to sit undisturbed for 24 hours andthen the plywood was removed from the water. The FTIR of the water fromthe leaching experiment showed a slight peak @ 800 cm⁻¹. The peak wasnot strongly defined as in the case of the silane reference peaks. Thetreated plywood showed no sign of silanes on the surface after beingsoaked in water for 24 hours. It did, however, readily repel water onall sides. The cut surface also repelled water even though it was neverin direct contact with the preservative composition. It was ½ inch to ¾inches away from the preservative composition.

There were several benefits that were observed for using a solvent, suchas THF, over just a neat application of methyltrichlorosilane,including: (1) costs were reduced by dilution (e.g., with THF) of theneat methyltrichlorosilane solution; (2) no evidence of an exothermicreaction was observed; (3) no white residue was left on the surface ofthe treated wood; (4) boron and silane readily penetrated into anddiffused through the wood and were delivered in one step; (5) little orno drying time was necessary prior to use; (6) cycle treatment time wasdrastically reduced over the CCA process; (7) no delamination ordegradation of plywood was observed; (8) the treated wood was renderedwaterproof; (9) the treated wood was rendered insect resistant (byvirtue of the boron present); (10) the treated wood was rendered fireresistant (by virtue of the boron present); (11) the treated woodresisted leaching.

In order to determine the boron penetration and retentioncharacteristics of the preservative composition of the presentinvention, an experiment was carried out as described in Example VI,below:

EXAMPLE VI

In a 2 liter Erlenmeyer flask, 800 milliliters of THF was added. Amagnetic stirring bar began stirring at a low rate. To this stirredsolution, 6.895 grams (0.7 percent by weight of solvent) of B₂O₃ wasslowly added. The mixture was allowed to stir for 20 to 30 minutes. Thesolution was clear, although some undissolved B₂O₃ did remain on thebottom of the flask. To this stirred solution, 200 milliliters ofmethyltrichlorosilane was transferred via nitrogen pressurized canula,over a 10 minute period. The system was well behaved and no evidence ofan exothermic reaction was observed. This resulted in an approximate 20volume percent methyltrichlorosilane solution. The solution was stirredfor 10 minutes and then stirring was ceased. A small amount ofundissolved B₂O₃ remained on the bottom of the flask. A 500 milliliteraliquot was decanted into each of two 1 liter beakers and covered with alarge watch glass. A first set of wood blocks had the dimensions of 1inch×2 inches×⅝ inches. A second set of wood blocks were ¾ inch cubes.The wood blocks from each sample were placed individually into theirrespective solutions. A smaller watch glass was placed inside the beakersuch that the weight of the watch glass kept the wood block samplescompletely submerged. The samples were allowed to stand in the solutionfor 1 hour. Some bubbling took place throughout the entire process.After the 1 hour treatment, the wood block were removed from thesolution and allowed to air dry overnight. The pieces of wood appearedto “smoke” while drying. The smoke was believed to be hydrochloric acid.It is probably produced from the hydrolysis of the unreactedmethyltrichlorosilane present on the surface of the wood. The solutionappeared turbid and slightly discolored following the treatment.

It was observed that one hour is probably too long to expose the wood tothe preservative composition as described above. The treated wood has atendency to smoke (i.e., evolve HCI) due to excess silane on the surfaceof the wood. A 5 to 10 minute exposure to the preservative compositionas described above is probably more than sufficient to achieve theafore-mentioned benefits.

Additionally, the appearance of the wood treated with the preservativecomposition as described above for 1 hour is gray or ashen inappearance. This is probably due to the boron. This feature is notpresent in the material treated for 5 to 10 minutes with thepreservative composition as described above.

In accordance with an alternative embodiment of the present invention,the boron-containing material is preferably impregnated into the woodproduct prior to, and separately from, impregnation by thesilane-containing material.

It was observed that the most effective method for introducing boroninto the wood product, at a concentration of 1 weight percent or greater(based on the total weight of the treated wood product), is with the useof water as the solvent, as opposed to hydrocarbons such as THF, andpreferably under the influence of a pressurized treatment vessel.

Although THF was used initially as a solvent for the boron-containingmaterial because it is commonly used in boron chemistry, the problem isthat boron is marginally soluble in THF and repeated treatment cyclesmust be used in order to reach 1 weight percent boron loading in theuntreated wood product. Accordingly, because of the differences in thetypes of solvents needed, it is preferred that the boron-containingmaterial be introduced into the wood product prior to, and separatelyfrom, the introduction of the silane-containing material into the woodproduct.

Following a four hour treatment period with the boron-containingmaterial/water solution, this should result in a final boronconcentration of 2 weight percent. It should be noted that higher boronloading concentrations could be achieved by varying (e.g., increasing)the boron concentration in the boron-containing treatment solutionand/or by varying (e.g., increasing) the treatment period. It was thendetermined whether the wet, treated wood product (i.e.,boron-impregnated) could be subsequently treated with thesilane-containing material (e.g., methyltrichlorosilane solution) toyield acceptable results.

In accordance with an alternative embodiment of the present invention,it was observed that the performance and cost of the pentane solvent issuperior to that of THF for the purpose of applying themethyltrichlorosilane to the wet, boron-impregnated wood product.

By way of a non-limiting example, a preferred concentration ofmethyltrichlorosilane in pentane, wherein the methyltrichlorosilane ispresent at 1 to 3 volume percent, should be used in the treatment ofboron-impregnated wood products. For example, thick wood products suchas railroad ties may require higher levels of the methyltrichlorosilaneto be present, whereas thinner wood products, such as planking forfences and decks and dimensional lumber, may require lower levels of themethyltrichlorosilane to be present. However, at least one exposed(untreated or unpainted) surface will generally be necessary in order tointroduce boron-containing materials into pre-existing woodenstructures.

In order to determine the silane penetration characteristics of thealternative methodology on treated (i.e. boron-impregnated) woodproducts, an experiment was carried out as described in Example VII,below:

EXAMPLE VII

Initially, a 1 volume percent solution of methyltrichlorosilane/pentanewas prepared and applied to a piece of wood saturated with water. Asecond solution, with a 3 volume percent concentration ofmethyltrichlorosilane/pentane, was also prepared and tested. Twoseparate pieces of water-saturated wood were sprayed immediatelyfollowing the removal of the wood from a boron-containing treatmentvessel. The wood pieces had been previously treated with the pressurizedaqueous solution of boron-containing material for 2 hours. The wood didnot appear to repeal or bead water immediately following the treatment.However, as the wood dried, it displayed evidence of complete waterrepulsion. Following a 24 hour drying time, the exterior of the 1 volumepercent solution treatment indicated partial waterproofing capability.No observable coating was evident on the surface of the wood. Followinga 24 hour drying time, the exterior of the 3 volume percent solutiontreatment was completely waterproof. Upon breaking the wood in half andexposing an interior surface, the penetration of the silane was evidentat the thickness of a human hair. Better results were obtained whenadditional wood pieces were treated with the 3 volume percentconcentration of methyltrichlorosilane/pentane solution in timeintervals of 30 minutes, 2.5 hours, 1 week, 2 weeks, and 4 weeks, afterremoval of the sample wood pieces from the boron-containing treatmentvessel. This may indicate that it may not be possible to treat totallywet wood, and it may be necessary to partially dry the wood prior to theapplication of the methyltrichlorosilane/pentane solution.

The performance of the solvent pentane appeared to be superior to THFwhen applying the methyltrichlorosilane to the treated wood. Thereactivity of the methyltrichlorosilane was reduced and no appreciableamounts of hydrochloric acid (HCI) gas was observed following treatment.This may be due, in part, to the fact that the silane was present inconcentrations of 3 volume percent or less.

Furthermore, when sprayed topically on the surface of a latex paintedpiece of wood, the methyltrichlorosilane/pentane solution penetrates thepaint layer and effectively seals the wood layer below the paintsurface. When sprayed topically on the surface of an oil-based paintedpiece of wood, the methyltrichlorosilane/pentane solution penetrates thepaint layer and effectively seals the wood layer below the paintsurface.

In order to determine the silane penetration characteristics of thealternative methodology on wood products having painted surfaces, anexperiment was carried out as described in Example VIII, below:

EXAMPLE VIII

A 3 volume percent solution of methyltrichlorosilane/pentane wasprepared and introduced to a 1-gallon plastic pump sprayer. Thissolution was then sprayed topically on the surface of latex andoil-based painted blocks of wood. A single pass spraying resulted in theincorporation of the silane beneath the surface of the paint. Extensivespraying appeared to reduce the thickness of the latex paint. Thepenetration was observed approximately 1 inch deep into the wood matrix.No amount of spraying appeared to diminish the thickness or adhesion ofthe oil-based paint on the surface of the wood.

The waterproofing penetration of the 1 volume percent solution ofmethyltrichlorosilane in pentane is preferably 0.75 inches, and thewaterproofing penetration of the 3 volume percent solution ofmethyltrichlorosilane in pentane is preferably 1.5 inches.

In order to determine the silane penetration characteristics of thealternative methodology on untreated wood products, an experiment wascarried out as described in Example IX, below:

EXAMPLE IX

Both of the 1 and 3 volume percent methyltrichlorosilane/pentanesolutions were applied to fresh red oak blocks in order to determine thepenetration ability of the solutions. A quick single spray pass wasapplied to each block of wood. The waterproofing penetration of the 1volume percent solution of methyltrichlorosilane in pentane was 0.75inches. The waterproofing penetration of the 3 volume percent solutionof methyltrichlorosilane in pentane was 1.5 inches. The level ofpenetration was determined by splitting cross-sectional pieces of woodoff of the block and then introducing the wood sample to a small streamof water. The boundary of the treated and untreated wood could then bedetermined.

Accordingly, it is preferred that the 1 and 3 volume percentmethyltrichlorosilane/pentane solutions penetrate and waterproof thewood to at least 0.75 inches and to at least about 1.5 inches,respectively, with a steady one-pass application. It may be possible tohave to spray and treat only one side of a wooden structure (e.g., afence), because the wood is generally in the dimension of a 1 inch×6inch board.

The foregoing description is considered illustrative only of theprinciples of the invention. Furthermore, because numerous modificationsand changes will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and processshown as described above. Accordingly, all suitable modifications andequivalents that may be resorted to that fall within the scope of theinvention as defined by the claims that follow.

1. A preservative composition comprising: at least one materialcontaining silane; at least one solvent; and wherein the at least onesolvent contains at least one of pentane, heptane, hexane, orcombinations thereof.
 2. A preservative composition as set forth inclaim 1 wherein the at least one material containing silane ismethyltrichlorosilane.
 3. A preservative composition comprising: atleast one material containing silane; and at least one solventcontaining pentane.
 4. A preservative composition comprising: at leastone material containing silane; and at least one solvent containinghexane.
 5. A preservative composition comprising: at least one materialcontaining silane; and at least one solvent containing heptane.
 6. Apreservative composition comprising: methyltrichlorosilane; and pentane.7. A preservative composition comprising: methyltrichlorosilane; andhexane.
 8. A preservative composition comprising: methyltrichlorosilane;and heptane.
 9. A preservative composition comprising:methyltrichlorosilane; and at least one hydrocarbon solvent.
 10. Apreservative composition as set forth in claim 11 wherein the at leastone hydrocarbon solvent is selected from the group consisting ofpentane, heptane, hexane, and combinations thereof.
 11. A preservativecomposition as set forth in claim 11 wherein the methyltrichlorosilaneis dissolved in a material selected from the group consisting ofpentane, hexane, heptane, and combinations thereof.
 12. A preservativecomposition comprising: at least one material containing silane; atleast one solvent; and wherein the at least one solvent consistsessentially of at least one of pentane, heptane, hexane, or combinationsthereof.
 13. A preservative composition comprising: at least onematerial containing silane; at least one solvent; and wherein the atleast one solvent consists of at least one of pentane, heptane, hexane,or combinations thereof.
 14. A method for protecting a wood product,comprising: providing a composition comprising at least one materialcontaining silane and at least one solvent; contacting the wood productwith the composition and penetrating and diffusing the silane into thewood product; and wherein the at least one solvent contains at least oneof pentane, heptane, hexane, or combinations thereof.
 15. A method forprotecting a wood product comprising: providing a composition comprisingat least one material containing silane and at least one solventcontaining hexane; and contacting the wood product with the compositionand penetrating and diffusing the silane into the wood product.
 16. Amethod for protecting a wood product comprising: providing a compositioncomprising at least one material containing silane and at least onesolvent containing pentane; and contacting the wood product with thecomposition and penetrating and diffusing the silane into the woodproduct.
 17. A method for protecting a wood product comprising:providing a composition comprising at least one material containingsilane and at least one solvent containing heptane; and contacting thewood product with the composition and penetrating and diffusing thesilane into the wood product.
 18. A method for protecting a woodproduct, comprising: providing a composition comprising at least onematerial containing silane and at least one solvent; contacting the woodproduct with the composition and penetrating and diffusing the silaneinto the wood product; and wherein the at least one solvent consistingessentially of at least one of pentane, heptane, hexane, or combinationsthereof.
 19. A method for protecting a wood product, comprising:providing a composition comprising at least one material containingsilane and at least one solvent; contacting the wood product with thecomposition and penetrating and diffusing the silane into the woodproduct; and wherein the at least one solvent consisting of at least oneof pentane, heptane, hexane, or combinations thereof.